Disclosed is an aqueous clearcoat material for producing a waterborne urethane-based two-coat coating system, comprising at least one secondary polyacrylate dispersion having a polyacrylate glass transition temperature Tg≧20° C. and at least one hybrid polyacrylate-polyurethane dispersion with a weight ratio of the polyacrylate fraction of the secondary dispersion to the polyacrylate-polyurethane fraction of the hybrid dispersion of 1:1 to 4:1, and as curing agent at least one low-viscosity aminosulfonic polyisocyanate and an aqueous basecoat material for producing a waterborne two-coat coating system comprising at least one polyurethane dispersion, at least one hybrid polyacrylate-polyurethane dispersion, and at least one melamine resin. Also disclosed are a waterborne two-coat coating system comprising the clearcoat material and the basecoat material, a process for producing it, its use to coat a substrate, and substrates coated with it.